1. Field of the Invention
The present invention relates to a method for providing services realized by intelligent networks (IN) to a subscriber using transit telephone service based on an internet protocol (IP) network or to an originating call service from a terminal connected to an IP network in a network architecture in which an intelligent network and an IP network are connected.
2. Description of Related Art
In a public telephone network, various services are provided to the users by using the technique of the IN which can customize the service and provide service as quickly as possible. The IN is standardized by International Telecommunication Union Telecommunication Standardization Sector (ITU-T). In 1997, the IN capability set 2 was standardized (ITU-T recommendation: Q.1220-1228). The IN has a two-layer structure in which an intelligent layer is provided higher than a transport layer for performing basic call processing via a signalling network.
On the other hand, there is an active move afoot to utilize the IP network as a transit network to realize a cheap transit telephone service. A gateway having the function of converting voice to/from an IP packet and the address translating function of performing translation between telephone number and an IP address is connected between the transport layer and the IP network, thereby enabling voice service to be provided on the IP network. There is a case such that the address translating function exists not on a gateway but an independent server on the IP network.
The methods of providing an independent server on the IP network with the address translating function include the xe2x80x9cgatekeeper method specified in H.323xe2x80x9d which is in the process of standardization by ITU-T and the xe2x80x9cMGCP (Media Gateway Control Protocol) methodxe2x80x9d which is in the process of standardization by the IETF (Internet Engineering Task Force) as a standardization organization of internet technologies. Further, a concept of replacing a telephone network itself with the IP network has been announced.
In the transit telephone service realized by the present IP network, however, the address translating function is concentrated on a specific device. Consequently, it is difficult to increase the function. On the other hand, even if the address translating function is dispersed to a plurality of devices, no mechanism of controlling the devices exists in the transit telephone service realized by the present IP network. Thus, networkwide service cannot be provided.
At present, the xe2x80x9cGateway Location Protocol (GLP)xe2x80x9d as a method for linking the plurality of address translating servers has been started to be examined. The GLP is a protocol used to reduce a load on a server and exchanges address information so that a plurality of servers hold the same information.
Examination on a method of providing communication service by the cooperation between the service control function of the IN and the IP network has been started by ITU-T. A method of providing a service control gateway function between an IP network and the service control function of a public network, providing a call bearer gateway function between the IP network and switching system of the public network, and providing the IP network with the H323 gatekeeper function has been proposed.
The service providing method using the functions, however, has to be examined further.
In recent years, as the variety of communication services increases, it is desired that novel IP network public network linked telephone service realized by the linkage between the service control function of the IN and the IP network is provided.
For example, it is desired that the user can access services such as toll-free telephone service from a terminal using the IP networkxe2x80x94public network linked telephone service by utilizing the service control function of the IN. For this purpose, it is necessary to access the IN function at the time of conversion between telephone number and an IP address, so that an apparatus on the IP network has to send a service request to the IN service control function and receive a service request response including a call continuous processing method (destination).
As described above, however, since the present transit telephone service using the IP network cannot provide network-wide service, services realized by the IN cannot be provided for a subscriber of the transit telephone service using the IP network and for an originating call service from a terminal connected to the IP network.
It can be considered that information or function necessary for the service control function of the IN is given to a specific independent server on the IP network having the address translation function. When all the servers on the IP network are provided with the information of the specific server, however, information of all of the servers has to be changed each time the structure of the IP network is changed.
On the other hand, when a specific device (database) is provided with the function, a load on the specific device is concentrated. Consequently, it is difficult to increase the function. It is therefore desirable to disperse the information and functions necessary for the service control functions of the IN to a plurality of specific devices on the IP network.
It is an object of the invention to propose a method of accessing the distributed information.
In the GLP being examined by the IETF at present, all of servers have correspondence information between telephone number and an IP address with respect to basic calls.
In practice, it is devised so that the amount of the correspondence information does not become too large by, for example, putting correspondence information between telephone numbers and IP addresses out of a control domain together. When the control domain is enlarged, however, there may be a server which cannot deal with the correspondence information.
It is another object of the invention to assure the connectability by compensating the server which cannot deal with the correspondence information with the correspondence information which is closer to the perfection of another higher-performance server.
In the invention, a network structure as described hereinbelow is employed.
The structure has: a first telephone network comprised of a first transport layer having a plurality of switching systems to each of which first telephone network subscriber""s terminals are connected and a first intelligent layer connected to the first transport layer via an SS7; and a second telephone network comprised of a second transport layer having a plurality of switching systems to each of which a plurality of subscriber""s terminals are connected and a second intelligent layer connected to the second transport layer via an SS7.
The first and second transport layers are connected to first and second IP networks via first and second gateways (or a plurality of first gateways and a plurality of second gateways). Each of the first and second gateways has the function of performing conversion between voice and an IP packet. The first and second gateways are controlled by first and second servers, respectively. The first and second IP networks are connected to an IP core network. A third gateway managed by a third server is connected to the IP core network. A third IP network is connected to the third gateway and subscriber""s terminals are connected to the third IP network. The subscriber""s terminals are managed by the third server.
The first and second intelligent networks have first and second service control points each having a memory for storing service control information of each user. The first and second service control points are connected to the first and second servers via first and second service control gateways, respectively.
Each of the first and second servers stores correspondence information between telephone number and an IP address of a gateway, authentication information, and usable bandwidth information. The third server stores correspondence information between an identifier (telephone number information such as address specified by ITU-T recommendation E.164) of each of terminals managed by the third server itself and an IP address, authentication information, and useable bandwidth information and, further, has information and function to start addition service provided by the IN. The first, second, and third servers construct a virtual IP control network and periodically exchange number information among them.
The correspondence information between the identifiers of the terminals managed by the third server and the IP addresses is classified into a class in which the IP address information of a device corresponding to the identifier can be unconditionally determined and a class in which the IP address information cannot be unconditionally determined. To the class in which the IP address information cannot be determined, an interrogation request is multicasted to the first and second servers, so that the range is made associated with the IP address. The range of the multicast is not limited to the above.
When an admission request signal is received prior to a call signal from a subscriber""s terminal connected to the third IP network, the third server discriminates the class of destination number designated by the terminal. Specifically, the third server determines whether a specific number string (such as 0AB0, 0A0C, 0ABC) is included in the number information or not.
When the specific number string is not included in the destination number, the destination number is in the class in which the address information of a corresponding device can be unconditionally determined. In this case, the third server collates the destination number with the correspondence information between the identifier of the terminal managed by the third server itself and the IP address, derives the IP address information of the server managing the gateway to which the destination terminal is connected or the IP address information of the gateway, and transmits a response signal including the obtained information to the subscriber""s terminal as a source terminal.
When a specific number string is included in the destination terminal number, it relates to the class in which the address information of a corresponding device cannot be determined. In this case, the third server multicasts an interrogation request to the first and second servers and notifies the subscriber""s terminal as a source terminal of the IP address information of the server which has responded. The address information is used to specify the destination of a subsequent call setup request signal.
When a response signal to the multicasted request is received, the third server stores the address information included in the signal into a memory for a predetermined period. When similar service request is received from a terminal managed by the server within the predetermined period, a subsequent process is performed by using the stored information.
The terminal which has received the response signal including the information of the destination of the call setup request signal transmits the call setup request to the server or gateway on the basis of the received information. When the server which has responded to the multicasted request receives the call setup request from the terminal, the server checks whether the received signal requires the start of the IN function or not. When it is determined that the received signal requires the start of the IN function, the server obtains the IP address information of the service control gateway from the information stored in the memory and transmits a service request to the service control gateway.
The service control gateway transmits a service request to the service control point by using the prestored information regarding the service control point. The service control point which has received the request notifies the server of the service information corresponding the received information via the service control gateway. The server selects a proper gateway from the first and second gateways on the basis of the information received from the service control gateway and transmits a call setup request to the selected gateway.
By enabling the terminal using the IP-public network linked telephone service to access the service control point via the service control gateway directly from the server or via another server by using the information stored in the server, various services (such as toll-free telephone service) provided on the public telephone network can be provided also to the user using the IP network. The information of the server having the function of accessing the service control gateway is not provided as fixed information but is discriminated by the multicast, thereby enabling the concentration of load on a specific server to be avoided and enabling a change in the network structure to be flexibility dealt with.
By employing the method of obtaining information which cannot be derived by the conversion using the IP addressxe2x80x94telephone number correspondence information in the server by multicasting a request to other higher-performance servers, the IP telephone with high connectability can be realized even by a low-performance server.